Move the Common Widths into a Sass list

Makes it easier to add custom percentage widths by using a Sass list to
store them like an array that we then loop over. Keeps configuration and
customisation inside the config file, and grid building in the grid
file.
Merge pull request #17 from quagliero/cloudy

Move the Common Widths into a Sass list
Fix main filename in bower.json
fixed sass loop for the common widths
Merge pull request #18 from momoiroshikibu/master

Fix main filename in bower.json
Output two css files
Merge pull request #20 from jshawl/output-two-css-files

Output two css files
updated bower and index